1. Field of the Invention
This invention relates generally to centrifuges, to centrifuges for processing drilling fluids or muds, and to methods of their use.
2. Description of Related Art
Centrifuges used in the oil industry process drilling fluids known as “mud” to separate undesired drilling solids from liquid mud. Some centrifuges, because of their continuous operation, have the advantage of being less susceptible to plugging by solids. Also, they may be shut down for long or short periods of time and then restarted with minimum difficulty, unlike certain centrifuges which require cleaning to remove dried solids. Often the solids/liquid mixture is processed at high feed rates.
To accommodate high feed rates, high torques can be encountered, much energy is required to process the mixture, and the centrifuge can be of considerable size.
When such a centrifuge is used to process drilling material (drilling fluid with drilled cuttings therein), changing mud flow conditions often require a human operator to frequently adjust centrifuge pump speeds to optimize centrifuge treating performance. Centrifuge operation can be a compromise between high performance and long intervals between maintenance and repair operations.
In some instances, a centrifuge is used in an effort to control the plastic viscosity of mud. A desired plastic viscosity is a function of the type of mud (water, oil, synthetic-based), the mud density, and other variables. When mud viscosity is too high, the feed pump is run faster; when mud viscosity is too low, the feed pump is run slower or turned off. Often mud properties are measured only periodically, resulting in a saw-tooth effect on the mud viscosity.